1. Field of the Invention
This invention relates to a photosensitive resin composition, more particularly to a photosensitive resin composition for a black matrix of a color filter. This invention also relates to a black matrix formed from the photosensitive resin composition, a color filter including the black matrix, and a liquid crystal display device including the color filter.
2. Description of the Related Art
In order to enhance contrast ratio and display quality of a liquid crystal display device, a black matrix is usually disposed in the gaps formed among stripes or dots of a color filter so as to avoid reduction of the contrast ratio and the color purity due to light leakage among the pixels. A vapor deposited film containing chromium or chromium oxide is used for forming the black matrix. However, there are problems of complicated process and costly material. Therefore, it has been proposed to form the black matrix using a photosensitive resin composition via photo-lithographic technology.
JP 2000-047378 discloses a photosensitive resin composition for forming a black matrix. The photosensitive resin composition includes an alkali-soluble resin obtained by the condensation reaction of phenol with aldehyde, an acid-crosslinkable methylolated melamine compound, a photoacid generator, a black pigment, and a dispersant. A specified dispersant is used to improve display quality of the photosensitive resin composition which contains a high amount of the black pigment so as to enhance pattern resolution of the black matrix.
JP 2008-268854 discloses a photosensitive resin composition for forming a black matrix. The photosensitive resin composition includes an alkali soluble resin having a carboxylic acid residue and a polymerizable unsaturated group in one molecule, a photopolymerizable monomer having at least one ethylenically unsaturated bond, a photo-initiator, and a black pigment. A specified alkali soluble resin is used to improve pattern resolution of the black matrix formed from the photosensitive resin composition which contains a high amount of the black pigment.
JP 2009-145432 discloses a photosensitive resin composition for forming a black matrix. The photosensitive resin composition includes a resin, a monomer having an ethylenically unsaturated double bond, a photo-initiator, and a pigment. The resin is a heat curable resin, a photosensitive resin, a thermoplastic resin, or combinations thereof. The amount of the black pigment in the total solid of the photosensitive resin composition is controlled so as to improve photosensitivity and development of the photosensitive resin composition containing a high amount of black pigment in a lithographic process.
In order to satisfy the high light-shielding requirement for the black matrix, the amount of the black pigment is increased in the art. However, the black matrix thus formed may have unsatisfactory surface smoothness and inferior stability of surface resistance after heating.
In view of the aforesaid, it is required in the art to provide a photosensitive resin composition for forming a black matrix which has a high light-shielding effect while obtaining superior surface smoothness and better stability of surface resistance after heating.